Pressure-reducing valve

1. A pressure-reducing valve in which a peripheral edge part of a diaphragm is clamped between a body housing a valve mechanism and a diaphragm cover fixed to the body, the diaphragm forming a pressure action chamber between the diaphragm and the body and forming a spring chamber between the diaphragm and the diaphragm cover, a spring housed in the spring chamber is provided in a compressed state between the diaphragm cover and the diaphragm, and a diaphragm rod connected to a central part of the diaphragm is connected to a valve body of the valve mechanism, wherein the diaphragm is formed from a disk-shaped rubber sheet and a sheet thickness of at least the peripheral edge part of the diaphragm is uniform in a natural state, the diaphragm cover integrally has a bottomed cylindrical portion having an end wall portion in an end part opposite the diaphragm and a collar portion protruding radially outward from an open end of the bottomed cylindrical portion, the body is formed with a clamping face holding the peripheral edge part of the diaphragm ( 28 ) between the clamping face and the collar portion, the clamping face has a chamfered portion positioned radially outward on an outer periphery of the clamping face with the peripheral edge end part of the diaphragm extending over the chamfered portion, the diaphragm cover is fixed to the body radially outward of the chamfered portion and the peripheral edge part of the diaphragm is compressively held between the clamping face and the collar portion at a position radially inward of the chamfered portion.

2. A pressure-reducing valve in which a peripheral edge part of a diaphragm is clamped between a body housing a valve mechanism and a diaphragm cover fixed to the body, the diaphragm forming a pressure action chamber between the diaphragm and the body and forming a spring chamber between the diaphragm and the diaphragm cover, a spring housed in the spring chamber is provided in a compressed state between the diaphragm cover and the diaphragm, and a diaphragm rod connected to a central part of the diaphragm is connected to a valve body of the valve mechanism, wherein the diaphragm is formed from a disk-shaped rubber sheet and a sheet thickness of at least its central part is uniform in a natural state, the diaphragm rod is provided coaxially and integrally with a shaft portion passing through the central part of the diaphragm so as to form an annular step portion facing toward the diaphragm side on the pressure action chamber side, the diaphragm has its central part abutting against a first retainer on the pressure action chamber side, the first retainer being formed in a ring shape so as to allow the shaft portion to be passed through and having an annular seal member disposed between the first retainer and the step portion, the diaphragm has its central part abutting against a second retainer on the spring chamber side, the second retainer being formed in a ring shape so as to allow the shaft portion to be passed through and clamping the central part of the diaphragm between the second retainer and the first retainer, a nut is screwed around a male thread cut in an outer periphery of the shaft portion, the nut holding the second retainer, the diaphragm, the first retainer, and the seal member between the nut and the step portion, and a gap between the first and second retainers has a minimum gap section and a maximum gap section which are defined by forming an inclined face on one of the first and second retainers, the minimum gap section being positioned further outward in a radial direction of the diaphragm than the maximum gap section, and the diaphragm is compressed at the minimum gap section.

3. The pressure-reducing valve according to claim 2 , wherein a groove having a substantially V-shaped cross-section is formed in at least one of a face of the first retainer on the diaphragm side and a face of the second retainer on the diaphragm side so that part of the diaphragm sinks into the groove.

4. The pressure-reducing valve according to claim 2 or 3 , wherein central parts of the first and second retainers which are made of metal, are abutted against each other directly or via a metal washer at faces which extend orthogonally to an axis of the diaphragm rod.

5. The pressure-reducing valve according to claim 1 , wherein the sheet thickness of the diaphragm at a peripheral edge part is uniform in a natural state, the diaphragm cover integrally has a bottomed cylindrical portion having an end wall portion in an end part opposite the diaphragm and a collar portion protruding radially outward from an open end of the bottomed cylindrical portion, and in a state in which the diaphragm cover is fixed to the body with the peripheral edge part of the diaphragm compressively held between the collar portion and a clamping face formed on the body, and a gap between the collar portion and the clamping face has a minimum gap portion and a maximum gap portion, the minimum gap portion being positioned radially inward of the maximum gap portion.